1. Field of the Invention
The present invention relates to a data access device, the control method thereof and a data access system, especially to a memory card access device, the control method thereof and a memory card access system.
2. Description of Related Art
A general electronic device often reads data from a storage device for system start-up or operation during a reboot process (a.k.a. hot start-up), a boot process (a.k.a. cold start-up) or a normal operation. There is a great chance that the data in demand are stored in discrete addresses of the storage device; therefore, the speed of start-up or data reading operation of the electronic device will be highly dependent on the random data access rate at which the storage device is able to function.
Generally, a common storage device could be a traditional hard disk drive (HDD) working with a mechanical spindle or a solid state disk (SSD) using flash memory as the storage medium. The traditional HDD has the advantages of large storage volume and low cost, but has a worse performance in reading random data, so that it needs long time to complete a start-up procedure or reading random data. In comparison with HDD, SSD has the advantages of small size, low power consumption and high data access rate, but the cost thereof per unit storage volume is relatively high, so that it is hard for SSD to be widely dispersed. In view of the above pros and cons, in order to accelerate the start-up procedure or the rate in reading random data in a cost-effective way, some uses a traditional HDD of large volume as a main storage device and uses a SSD of small volume as a cache device at the same time. This solution often adopts the Native Command Queuing (NCQ) function of the known Advance Host Controller Interface (AHCI) protocol to accelerate the access rate; however, most devices supporting the AHCI protocol are Serial Advanced Technology Attachment (SATA) devices, which means that this solution is limited to accessing data through a SATA interface while the problem of high cost due to using a SSD still exists. There is another solution to support data cache through a HDD with a built-in flash memory; however, this kind of Hybrid HDD costs much more than a traditional HDD of the same storage volume, and thus remains unpopular to electronic device manufacturers who usually take the cost as the first concern.